I am bemused by the number of people who seem less upset by Kyuubee’s morals in Puella Magi Madoka Magica than by his “entropy” explanation in Episode 9. Nerdy and spoilerish discussion follows.

Jason is upset that the explanation is not consistent with the Second Law of Thermodynamics (entropy increase.) But that seems to miss the whole point.

This is a show about magical girls. As in M-A-G-I-C. I have read some fantasy stories in which magic was constrained to follow the First Law of Thermodynamics (energy conservation), for example Patrick Rothfuss’s Kingkiller Chronicles series, but even Rothfuss doesn’t require magic to obey the Second Law. I would say it’s pretty much a matter of definition: anything that is worth calling “magic” must violate the Second Law of Thermodynamics, and vice versa.

You may of course simply deny that the emotions of pubescent girls are powerful enough to overcome such a fundamental natural law. That seem to be Jason’s position. But if so he should have bailed out at the first episode when it became obvious that magic was being used. Once you accept magic, the Second Law is pretty much out the window.

DarkMirage and Kurogane seem less concerned with the Second Law violation than with the inefficiency of Kyuubee’s methods. I don’t find these arguments very convincing.

First, it is argued that Kyuubee could just use time travel as a more efficient energy source. At the moment it seems that Homura can travel in time, but it’s not clear that Kyuubee can. Even if he can, physicists generally agree that true time travel requires a violation of the Second Law. So Kyuubee can use time travel only by making use of magical girls, and we are back where we started.

(DarkMirage’s argument has an interesting implication: if you have a violation of the Second Law, you can probably leverage it into a violation of the First Law. This might help explain how a small number of magical girls can produce the tremendous amounts of energy Kyuubee needs. He only needs a relatively small amount of entropy reversal to get started, and can use that to generate as much energy as he needs.)

DarmMirage also suggests that it would be much more efficient to set up “loli farms.” I have my doubts about that. Experience shows that only a tiny percentage of plants and animals are suitable for domestication. (Jared Diamond provides a detailed exposition.) Bear meat is allegedly delicious, but it would be foolhardy to try to raise grizzlies for food. Elephants are very useful, but for thousands of years humans have found it more practical to capture them in the wild and tame them, rather than to breed them in captivity. I’m fairly sure that any attempt to raise magical girls would run into similar problems.

Furthermore it is implied that only a tiny minority of girls have the emo power necessary to become magical. If magical girls don’t breed true, than it would be pointless to try to domesticate them, even if the other obstacles could be overcome.

A point worth noting: as powerful as Kyuubee is, his power depends ultimately on exploiting the power of magical girls. This implies that magical girls may be able to do things that Kyuubee can’t do.